The Wonderful New Closed-Loop Pump: The Medtronic 670G

As a person with type 1 diabetes, I have struggled over time with the eternal battle: how to keep blood glucose and insulin in balance. Like my fellow type 1s, I have grappled with mastering basal and bolus doses.

I always wonder, is this the right dose for a given meal? How much should I inject? When we give ourselves insulin to cover the food we eat, sometimes it works. Sometimes it doesn’t. And sometimes it’s a wild ride, and we hold on for dear life!

Along comes the newest thing in town: the Medtronic 670G pump. For those of you who have not heard the buzz, it’s the first closed-loop insulin delivery system. That is, a continuous glucose monitor (CGM) that talks with a pump… and presto! Proper doses of insulin are administered! Some folks call it the first “artificial pancreas.” I call it a miracle!

How does the system work? Basically, the CGM transmits regular messages to the pump, which in turn runs through a complex algorithm to determine, every five minutes, exactly how much insulin to administer. For a detailed description of the mechanics, please go to the Medtronic website.

Like all inventions, the new sensor/pump duo has its pros and cons. Let me start with the positives as I see them because they far outweigh the negatives for me.

The Pros

The first positive is amazing blood glucose control. Yes, that’s the bottom line, isn’t it? The closed-circuit sensor/pump combo does what injections cannot. The system keeps you in proper range some 80 to 95% of the time. Formerly, with injections, I was lucky to stay in range 70% of the time.

Worried about hypoglycemia? It’s still a concern, but way less. For me, hypoglycemic events are few and far between and far less intensive. The system stops administering insulin before you become low.

With no background long-acting basal insulin, there is less “downward“ pressure on glucose levels. So when I do become hypoglycemic, I don’t nose-dive as I did before. I enter hypoglycemic territory gradually and safely.

Also, far less correction is needed. Whereas I used to have to counter the drop with a half bottle of apple juice, cookies, or more, now just a few small candies will do the trick.

Hypoglycemia is nicely managed. If I skyrocket, as I sometimes do occasionally on the new system, the pump offers insulin corrections in segments. No more nosediving due to too much corrective insulin by injection. Everything happens more gradually. The pump settings keep everything in line.

Nightime is a dream. If I can get my blood sugar settled down after dinner, nearly every night is very different than the old days. No more highs and lows or alarms. The insulin drip finds its way beautifully to about 120 or 125 mg/dL and stays there all night. What a difference from injections that create extreme highs and lows and panic during the night.

Okay, this may not seem important, but there are no more needles! For us type 1s, needles are no big deal. We are as used to them as we are seeing the sunshine. But imagine a world without them. Yes, no injections! I’m not complaining about that!

When you go out during the day, there is very little to take along. You do need your blood sugar testing kit, but that’s about it.

When I wear the pump on my belt, I can just peek down and push the button and see what my numbers are. But I’m not surprised to see very little change! Once I am an hour or two post-prandial, the line is just amazingly steady.

Most remarkably, Medtronic claims that the system continues to adapt to you. So as it delivers insulin every day, it makes automatic adjustments in the quantity and times of delivery. Eventually, you and the machine are in nearly perfect sync!

A word of caution. Just because the pump performs so well does not mean that you can throw caution to the wind. The old guideline about fewer carbs being better than more carbs at mealtime still applies. Unreasonable food consumption can still create major spikes.

Similarly, care must be taken on the low side. For example, if you ask for a bolus before a meal, but don’t eat, you need to take steps to see that too much insulin is not administered. You’ll learn about how to do that when you’re on the pump. And when exercising, the pump advises setting a target of 150 mg/dL rather than 120 mg/dL to stay away from troublesome lows.

MiniMed 670G and Guardian3 CGM sensor from Medtronicdiabetes.com

The Cons

Are there downsides to this delightful scientific wonder? Yes indeed, but they are minor aggravations.

First, the whole system is very dependent upon constant fingerpicking. It is not uncommon for me to do anywhere from four to ten fingersticks a day to keep everything in line the way it should be.

Second, every third day you need to change out the infusion set, which is the needle that stays connected to your body and attaches to the pump. And every week you need to change out the sensor. Both require some paraphernalia and time.

The system requires quite a learning curve to get started. Medtronic recommends at least three full days of training before you can go to “auto mode.” The entire first week is all about learning how to use the pump in what is called “manual mode.”

Some critics are not happy with the gradual corrections that the system administers. For instance, if you are high, say around 270 to 280, the system might give you only one or two units of corrective insulin. This is clearly not enough to bring you down to the 120 range. Then you have to go back and do another blood sugar test and ask the system to give you more. It’s a bit frustrating, but the cumbersome procedure keeps you in safer ranges without the normal hypoglycemic plunge.

Another downside is complexity. Yes, you do eventually learn how the system basically works. But the whole operation is far from simple. It can take weeks to master. In the first month, you need to work closely with your Medtronic coach to tweak the system with setting adjustments.

With a few advanced educational degrees, you might master this thing in its entirety! Seriously, you need patience to get the system under good control.

My Conclusions

To summarize, I would recommend the new closed-loop system to people with type 1 diabetes. In my opinion, it is the best thing going on right now.

Will there be improvements on it? Without a doubt! Once competitors begin to enter the marketplace, the whole system will definitely be simpler and more efficient.

The system is still in its infancy. There are many improvements that will follow. Someday we will look back on the Medtronic 670G and laugh at its complexity, just as we look back at the primitive nature of early computers and cell phones.

But I for one am willing to venture into this new world even in its early stages. People with type 1 diabetes have been waiting forever for such an invention.

In summary, no type 1 should be without this modern wonder of science.

David has a Ph.D. degree in French literature and a history of teaching French at university and secondary levels. After a career in education, he went into business with his son. They created an educational video company that sold to schools throughout the U.S. After retirement, he took up bluegrass banjo, wood bowl turning, and fused glass artwork. He is a passionate reader, writer, and TV watcher. He has been diabetic for six years. He strives to learn more about type 1 so he can share his learning with fellow diabetics.

Comments

Thanks for the text. My 12y daughter, new to type 1 since a month back, has been offered the 670G. But she doesn’t want the tube into the body, and has decided (without too much talk with her medics team) that she want the omnipod instead . She feels that she might feel “less sick” mentally without the tube.

Do you have any thoughts about that? Obviously we parents are new to this as well 😉

As a tech-geek and worried father I think the 670G sounds like a good one… 😉 But can understand her reasoning, being that age and active with sports and friends.

Potential cost differences is out of the equation as we’re lucky to get any pump offered “for free”. 🙂

it’s has been good (most days). one thing the writer skipped over is that you have to bolus for meals and get fairly accurate carb counting done. if you are off a little the pump can compensate but not if you forget to bolus. second i find if very arrogant that any one, espically a T1D author would say “In summary, no type 1 should be without this modern wonder of science.” the great thing about a pump is it’s one of many options. i know enough T1Ds that have great control on 2-3 injection to mulit injection to just a pump, pump plus CGM and now the auto mode with the 670G. it’s one way to help control your BS not the only and not the standard that everyone needs. Yes, there are some changes that need to come and most definitely will. in a year or two the programs with be different and other options may be added. But it’s still a machine and you as a T1D need to be active and controlling in your own treatments.